Complex eyes in the Cambrian

I got a letter from a creationist today, claiming that "Darwinism is falsified," based on an article in Nature. It's kind of amazing; this article was just published today, and the metaphorical digital ink on it is barely metaphorically dry, and creationists are already busily mangling it.

It's a good article describing some recent fossil discoveries, found in a 515 million year old deposit in South Australia. Matthew Cobb has already summarized the paper, so I'll be brief on the details, but it's very cool. What was found was a collection of arthropod eye impressions, probably from cast-off molts. No sign of the bodies of these animals was found, suggesting that perhaps they were not fully sclerotized, or as the authors suggest, that disarticulated eyes were more prone to rapid phosphatization than eyes attached to a decaying body. There is no evidence of biomineralization, so these were animals with a very light armor of chitin alone.

What's wonderful about the eyes is that they are relatively large and contain numerous ommatidia, the individual facets of a compound eye. They have over 3,000 lenses, and there's also evidence of regional specialization in the eye. These were highly visual animals that were capable of forming a good image of the world around them.

Complex arthropod eyes from the Early Cambrian. a-d, Three fossils of compound eyes from a large arthropod from the Emu Bay Shale, South Australia (a-c), shown in similar hypothesized orientation to the compound eye of a living predatory arthropod, the robberfly Laphria rufifemorata
(d; anterior view of head). All fossil eyes have large central ommatidial lenses forming a light-sensitive bright zone, b, and a sclerotized pedestal, p. Because the fossil eyes are largely symmetrical about the horizontal axis, it is not possible to determine dorsal and ventral surfaces, and thus whether the eyes are left or right. All fossils are oriented as if they are left eyes (medial is to the left of the figure). In b there is a radial tear (white line) with the top portion of the eye displaced downwards to overlie the main part; extensive wrinkling causes some central lenses (arrow) to be preserved almost perpendicular to the bedding plane.

These eyes are also from the early Cambrian, so they appeared in the early stages of large animal evolution. The closest thing to them in ommatidial number are the sophisticated eyes of many trilobites, but even there, these eyes were early and relatively large.

Complexity of the Early Cambrian Emu Bay Shale eyes compared to eyes in other early Palaeozoic taxa. a, b, Number of ommatidia (a) and lens size (b) plotted against stratigraphic age for Cambro-Ordovician arthropods. The Emu Bay Shale eyes have many more ommatidia and much larger individual ommatidia than eyes in all other Cambrian taxa. Trilobites are plotted according to eye type: schizochroal eyes have relatively few, large lenses and are optically unusual compared to typical compound eyes.

Where in this is the refutation of evolution? I don't know. But I did receive a letter from that Canadian idiot, David Buckna, crowing about it, and linking to his very silly creationist article describing it, in which you'll find the abstract for the paper with curious random spastic boldfacing added which supposedly highlight the parts of the story that contradict evolutionary theory, words like "complexity" and "Cambrian explosion" and "more complex" and "great evolutionary event". It's a bit bizarre and like looking at the obsessive activity of a squirrel gathering nuts.

Here's the creationist summary of the paper, however.

The Cambrian explosion is affirmed; complexity appears suddenly without transitions; Darwinism is falsified; the inference to the best explanation is intelligent design. Let the world know.

Let's deal with each of these claims one by one.

The "Cambrian explosion" is a term coined by scientists to describe the rapid (in geological terms) appearance of large, complex animals with hard skeletons over the course of a few million years roughly half a billion years ago. There is no creationist gotcha in pointing out the existence of this geological period; scientists have written whole books on the subject.

The sudden appearance of complexity is no surprise, either. We know that the fundamental mechanisms of eye function evolved long before the Cambrian, from the molecular evidence; what happened here was not that, poof, eyes instantly evolved, but that the evolution of body armor gradually increased from the pre-Cambrian through the Cambrian, making the organization of eyes visible in the fossil record.

It is also the case that the measure of complexity here is determined by a simple meristic trait, the number of ommatidia. This is not radical. The hard part in the evolution of the compound eye was the development of the signal transduction mechanism, followed by the developmental rules that governed the formation of a regular, repeating structure of the eye. The number of ommatidia is a reflection of the degree of commitment of tissues in the head to eye formation, and is a quantitative difference, not a qualitative one.

And finally, there's nothing in the data from this paper that implies sudden origins; there can't be. If it takes a few hundred thousand years for a complex eye to evolve from a simple light sensing organ, there is no way to determine that one sample of a set of fossils was the product of millions of years of evolution, or one day of magical creation. It's a logical error and a failure of the imagination to assume that these descriptions are of a population that spontaneously emerged nearly-instantaneously.

"Darwinism" is not falsified. Darwin himself explained in great detail how one should not expect fine-grained fossil series, due to the imperfection of the geological record. Creatonists, read chapter 9 of the Origin; here's a brief excerpt.

It should not be forgotten, that at the present day, with perfect specimens for examination, two forms can seldom be connected by intermediate varieties and thus proved to be the same species, until many specimens have been collected from many places; and in the case of fossil species this could rarely be effected by palaeontologists. We shall, perhaps, best perceive the improbability of our being enabled to connect species by numerous, fine, intermediate, fossil links, by asking ourselves whether, for instance, geologists at some future period will be able to prove, that our different breeds of cattle, sheep, horses, and dogs have descended from a single stock or from several aboriginal stocks; or, again, whether certain sea-shells inhabiting the shores of North America, which are ranked by some conchologists as distinct species from their European representatives, and by other conchologists as only varieties, are really varieties or are, as it is called, specifically distinct. This could be effected only by the future geologist discovering in a fossil state numerous intermediate gradations; and such success seems to me improbable in the highest degree.

Finding a fossil eye with numerous ommatidia a hundred million years after molecular biology tells us that eyes evolved does not in any way falsify the idea of a gradual evolution of the eye.

Given that there is nothing in this story that contradicts the idea of a natural process generating increasing complexity over time, and given that it's an observation that fits perfectly comfortably within the body of evolutionary theory, there is no reason to leap the utterly unfounded conclusion that an invisible spirit zapped these fossils into existence — an invisible spirit for which there is no evidence. Furthermore, what evidence is in this paper directly contradicts Buckna's beliefs: he is a young earth creationist, and this is a paper describing organisms that lived 515 million years ago. If you look at the chart I reproduced above, you might also notice that the pattern of complexity (ommatidial numbers) in trilobites shows a trend of increase over 80 million years.

I shall gladly let the world know that David Buckna is an irrational fool who doesn't know how to read a scientific paper and makes illogical leaps in his arguments.

I’ve always found it interesting that creationists can read enough of the literature to quote mine, without noticing what the literature is saying. I guess that they learn that skill by reading the Bible.

They have no capability of comprehension and no interest in comprehension. It’s an associative scheme: they scan through an article to spot “hot button” verbiage that they use to index into their cardfile of stock arguments.
The appropriate arguments are assembled into a “rebuttal”. It wouldn’t be hard to write a computer program to implement this algorithm.

It is possible, though I wouldn’t judge it likely, that somebody already has, and we are seeing the results.

AiG, the ICR, and the DI are continuously and breathlessly keeping their rubes “up to date” on how to interpret the latest research coming out of the scientific community by publication highjacking legitimate work and making it appear that ID/creationist exegesis is the proper way to understand science.

Then we see our copy/paste, FL/IBIG trolls engaging in these same mechanical and repetitive behaviors. So the ID/creationist tactics have certainly worked in turning these trolls into automatons.

Oh please, all eyes are apparently related, and thus would have to have a common ancestor that existed well before the Cambrian “explosion.” So why wouldn’t complex eyes exist at the start of the Cambrian?

It’s just the same old boring “Cambrian explosion = God Designer.”

The Cambrian was an amazing radiation produced when spiking oxygen levels allowed animals to become dramatically larger and to otherwise evolve to fit niches. Plants were nowhere to be seen, and land animals were absent, or, at best, small and unimpressive.

Eden makes sense as design. Prokaryotes for at least a billion years, then Eukaryotes for another billion or so prior to multicellular animals, then the Ediacaran radiation which largely died out (why, Designer?) and a few other feints, and then finally the Cambrian “explosion” where a huge number of phyla are first visible–a number to become extinct relatively soon (why, Designer?)–is not design, at least none that we know.

What’s fascinating is that their version flies in the face of all sciences (including that which they use to share their ‘message’ on the internet).

They haven’t figured out that simple systems can give rise to insanely complex products in a very short period of time. Using computers we can do in hours what it takes a team of trained engineers a week to do. But even before that, we could watch complex systems emerge from simple behaviors in real time.

I’ve always found the obsession with increasing complexiy interesting. A lot of things actually decrease in complexity as evolution occurs. After all, you start with a crude system that kind of does the job, then work toward a system that does the job well. Increasing efficiency often means decreasing complexity as uneeded steps/parts are worked out of the method.

If you don’t believe me, you can read his books, that there are on-line:

Exactly how does the fact that Darwin was a fairly ordinary Victorian male chauvinist affect the validity of his research?

Any more than the validity of Ben Franklin’s electrical research – and he was a world-famous scientist for his era – would be changed by the fact that he owned slaves? (As, incidentally, did many of America’s Founding Fathers, including George Washington and Thomas Jefferson.)

Please, if you want to show that Darwin was wrong in his scientific insights – and he is known to have been wrong in a number of cases – such “ad hominem” attacks miss the target. You need something better. One suspects you use the ad hominems because you don’t have anything better.

Darwin was wrong about lots of things. That doesn’t mean that he wasn’t a scientist. It also doesn’t mean that he was wrong about everything. That criteria only applies to those who claim to be omnipotent, not scientists.

goliardo said: How can you quote Darwin for anything???? Darwin was not a scientist!!!

Neither are you. And Darwin’s been dead for over a century - things were different then. You worshippers of willful ignorance and scientific illiteracy should realize that the world has moved on since Darwin…even if creationists haven’t.

Any real discovery that conforms to modern evolutionary theory automatically disproves Darwinism.

Look at it this way. If you have ever collected data points and calculated a best-fit line you’ll know what I mean. Note that none of the points fall exactly on the line, so with each new data point you show everyone how far it is from the line. Thus each point “falsifes” the line, and the more points the better. If your audience is gullible enough, you can even forget about all the previous points that were claimed to “falsify” the line, and pretend that this one is the “smoking gun.” If they don’t buy it, just pick another point that’s further from the line. Keep going until they give up. But never, ever mention how the points converge on the line, or that the convergence was neither sought nor fabricated. If you’re really good at it, you will know not to mention that others tried to force-fit the data into other, mutually contradictory lines.

Atheistoclast: thanks for attempting science, pitty about the unsubstantiated faith claim at the end:

‘and I have a pretty good idea about who or what that something is!’

‘Pretty good idea’? Not bad, but then you’re up against science which, ‘knows!’ Keep the the faith bandwagon rolling, and try not to trip up into too many manglings of your meaning. I mean, really, you don’t, ‘KNOW!’ I do, and I have no need for recourse to a god constantly checking to see if I washed my hands after visiting the shitter.

Don’t tell me, it’s the magic invisible hologram hypothesis, right? Or maybe the photons that are warped in the magnetic field of the earth, yea that’s it. Why don’t you google eyeless fruit flies and tell us all again how DNA has nothing to do with eyes and morphology.

nilsson & pelger showed that a patch of useful light-detecting cells is unstable - a depression produces a runaway process of deeper depression, and a lens structure that enhances the directional selectivity of the pit. it seems to me that a bulge will lead to more bulging and compound lenses for exactly the same reason. has anyone done similar calculations for this convex case?

If you don’t believe me, you can read his books, that there are on-line:

[Various quotes from the works of Charles Darwin referring to his sexist beliefs.]

Scientists are not infallible like prophets claim to be. Thus, we need not assume that because Darwin said something that turned out to be false and/or offensive that we can simply whitewash the error or the offense like religious bigots do their scriptures.

And for the record: We are NOT “Darwinists” and haven’t been for at least a century now. We are simply students or experts of biology, a branch of science, that, like all others, advances constantly and leaves behind ideas that prove unworkable or false, no matter who they come from.

Thus, science is by nature self-correcting in a way religion seldom ever is.

Atheistoclast said:

I will restate my belief that DNA does not encode such intricate morphological structures. You can rant on all you like about transcription factors and promoters but these just affect protein expression and regulation.Something else is responsible for this - and I have a pretty good idea who or what that something is!

You can take your entirely pointless “belief” and shove it back up your @$$, you liar.

The real issue for both creationist and evolutionist alike is explaining how such complex compound eyes with their thousands of lenses, each representing a pixel of vision, could have arisen through changes in DNA. Both would assume this to be the case.
The creationist believes it is God’s work whereas the evolutionist prefers natural selection instead. But both are mistaken.

I will restate my belief that DNA does not encode such intricate morphological structures. You can rant on all you like about transcription factors and promoters but these just affect protein expression and regulation.Something else is responsible for this - and I have a pretty good idea who or what that something is!

So if it wasn’t natural selection and it wasn’t God, who could possibly be manufacturing and sticking eyes on all the flies because that bit of their DNA is missing? No wait - don’t tell me! It’s Dr Dolittle, right?